Do the openings for cable trays between power and data transmission lines need to be sealed

Yes, openings for cable trays carrying power and data lines should be sealed to maintain fire safety, prevent electromagnetic interference, and ensure code compliance.Fire and Safety ConsiderationsOpenings where cables pass through walls, slabs, or panels must be tightly sealed using firestopping materials such as fire-rated boards, firestop packs, mastic, or mineral wool. This prevents the spread of fire, smoke, and heat through penetrations and preserves the building's fire-resistance rating. Large openings may require a fire-resistant backing plate before sealing, and all gaps around cables and metal trunking should be completely filled without visible cracks or voids .Electromagnetic Interference (EMI) and Data IntegritySealing is also important to maintain separation between power and data cables, which reduces EMI and prevents data corruption. NEC 2026 and TIA-569-E standards recommend using dividers, barriers, or compartmentalized trays when power and data lines share a pathway. Unshielded data cables typically require at least 12 inches of separation from power cables unless a listed barrier is used, while shielded data cables require 6 inches . Proper sealing at openings helps maintain these separations and prevents interference.Methods for SealingBrush strips or foam inserts allow cables to pass through while keeping the containment as airtight as possible, which is especially important in data centers to maintain cooling efficiency .Firestop packs or mastic can be used for wall or slab penetrations to ensure a tight, reliable seal .Cover plates should be square, properly sized, and painted evenly to close the opening and maintain both safety and aesthetics .SummarySealing cable tray openings is essential for:Fire protection and compliance with building codesMaintaining proper separation between power and data lines to prevent EMIPreserving airflow and cooling efficiency in data centers Using appropriate firestop materials and barriers ensures both safety and reliable system performance while meeting NEC and industry standards .